1. Field of the Invention
The present invention relates generally to an electronic torque tool, and more particularly to an electronic torque tool having discontinuous resettable torque warning values with an interval therebetween.
2. Description of the Related Art
An electronic torque tool such as an electronic torque wrench includes an electronic display screen and several pushbuttons. The display screen serves to show to a user the magnitude of the applied force (torque) in operation of the wrench. The electronic torque wrench also has a torque warning value. When the applied force of the wrench reaches the torque warning value, a warning effect is provided to remind the user to stop applying the force.
The user can adjust the torque warning value. In a torque setting mode, by means of the pushbuttons of the torque tool, the warning value can be increased or decreased and reset in accordance with the required tightening extent of different threaded structures.
When adjusting the torque warning value of the existent electronic hand tool, the torque warning value is continuously increased or decreased. For example, in the case that the current torque warning value of the torque wrench is 26 N/m, while the tightening requirement of the next threaded member is 34 N/m, then a user can press the pushbutton of the wrench to change the warning value. At this time, the warning value will continuously skip over 26, 27, 28 . . . 33 until the value of 34 is shown. After the torque warning value of 34 N/mis reset, when the applied force of the wrench reaches 34 N/m, the wrench will give a warning to the user.
Within the set range of the warning value, the warning value can be set any value. For example, the set warning value of the wrench can range from 11˜50 N/m. That is, any warning value within the range of 11˜50 N/m can be set to the wrench. In general, the torque warning value is set the required torque value of the threaded member to be tightened. With the above case taken as an example, the warning value is set 34 N/m, whereby when the applied force of the wrench reaches 34 N/m, the user will receive the warning.
However, due to operation inertia, when the user hears or feels the warning effect, the user can hardly immediately stop wrenching a work piece. Instead, the user will further wrench the work piece for a short period of time before stopping. In this case, the threaded member may be actually over-tightened by a tightening force of 36 N/m rather than the necessary 34 N/m.
Moreover, in operation, the user often needs to notice the warning signal so as to avoid over-tightening. This will prolong the operation time and affect the smoothness of the operation.